1. Technical Field
A wafer-scaled light-emitting device and manufacturing method thereof is disclosed, especially is related to a wafer-scaled light-emitting diode with narrow dominant wavelength distribution and a method of enabling convergent distribution of dominant wavelength of the wafer-scaled light-emitting device.
2. Reference to Related Application
This application claims the right of priority based on TW application Ser. No. 098106259, filed “Feb. 25, 2009”, entitled “LIGHT-EMITTING DEVICE WITH NARROW DOMINANT WAVELENGTH DISTRIBUTION AND METHOD OF MAKING THE SAME” and the contents of which are incorporated herein by reference in its entirety.
3. Description of the Related Art
The light-generating mechanism of a light-emitting diode (LED) is that the difference of the energy of electrons moving between an n-type semiconductor and a p-type semiconductor is released through the form of light. This light-generating mechanism of the LED is different from that of incandescent lamps so the LED is titled a cold light source. Besides, LED has advantages like high reliability, long life span, small dimensions, and electricity saving so the LED has been deemed as an illumination source of a new generation.
FIG. 1A to FIG. 1E show a conventional process flow of manufacturing a light-emitting device. As FIG. 1A shows, a substrate 10 is provided. As FIG. 1B shows, a plurality of epitaxial stacked layers 12 is formed on the substrate 10, and the plurality of epitaxial stacked layers 12 is etched by lithography to form a plurality of light-emitting stacked layers 14, as FIG. 1C shows. Next, as FIG. 1D shows, electrodes 16 are formed on the plurality of light-emitting stacked layers 14 to form an LED wafer 100. Finally, as FIG. 1E shows, the LED wafer 100 is diced to form LED chips 18.
The distribution of the dominant wavelengths of the light-emitting stacked layers 14, however, is not uniform. The difference of the dominant wavelength can be 15 nm˜20 nm or even more so the difference of the dominant wavelength of the LED chips 18 formed by the light-emitting stacked layers 14 is large as well. The problem of non-uniform distribution of the dominant wavelengths further influences the consistency of characteristics of the products utilizing the LED chips 18. Taking the conventional blue LED chip with the 460 nm dominant wavelength cooperating with the yellow phosphors to generate white light as an example, if the distribution range of the dominant wavelengths of the blue LED chips on the same LED wafer reaches 20 nm, namely the dominant wavelengths are between 450 nm and 470 nm, the distribution of the color temperatures of the white lights formed by mixing the light from the blue LED chips and the yellow wavelength-converting materials having 570 nm excited wavelength is also influenced.
As FIG. 2 shows, because the wide distribution of the dominant wavelengths of each light-emitting stacked layer on the LED wafer, the color temperatures of the white lights formed by mixing the light from the LED chips and the wavelength-converting materials distribute between 6500K and 9500K. With the difference of the color temperatures, which is about 3000K, the consistency of the quality of the products is affected significantly.
To solve the problem of non-uniform distribution of the dominant wavelength of the light-emitting stacked layers 14, there are probing, sorting, and binning processes in the conventional manufacturing process of the LED chips 18 to screen out the LED chips 18 having similar dominant wavelengths for various application demanding different wavelengths, as FIG. 3 shows.
Although the probing, sorting, and binning processes can reduce the influence upon the consistence of the quality caused by non-uniform distribution of the dominant wavelength, when the products to which the LED chips 18 are applied strictly require a tight distribution of the dominant wavelength, such as the back-light unit having the LED chips in the large size display, the ratio of the available LED chips 18 on the LED wafer 100 is low. Besides, sorting and binning processes are time-consuming and laborious, and increase the cost and time of manufacturing the LED chips.